This invention relates to a method and apparatus for sealably penetrating a moisture impervious thermoplastic sheet or liner, particularly suitable for lining reservoirs, hazardous waste disposal sites, outdoor fluid containment areas and other similar applications, without damaging the sealing characteristics of the liner. Specifically, the present invention relates to a plastic liner pipe penetration adapter designed in such a way as to also allow field testing of the sealability of the liner after the installation of the adapter.
Thermoplastic sheets or films have been utilized for environmental pollution control as a water barrier for the building of ponds, reservoirs, lagoons, landfills and as a soil sealant for hazardous or nuclear waste by laying the plastic sheeting along the ground with the seams welded or cemented by known methods. Various bentonite-containing sheet barriers also exist for use as liners for extremely large areas such as ponds, lagoons and hazardous waste sites.
Landfills, lagoons or other waste ponds are typically constructed by excavating land to create a reservoir area. If desired, berms can then be built around the perimeter of the reservoir area to extend the walls of the reservoir above ground level. Quite often, the landfill, lagoon or waste site is next lined with a layer of clay to serve as a barrier. Additionally, the excavated area can be graded in such a way as to create a declination towards one corner, end or area of the excavation.
Next, a thermoplastic liner is installed by, for example, placing flexible plastic sheets over the entire surface of the reservoir soil and berm area in an overlapping or abutting fashion, and then welding or cementing the sheets together to create a water impermeable liner. An exemplary method of welding plastic materials, such as plastic sheeting, is set forth in U.S. Pat. No. Re. 32,103 assigned to Gundle Lining Systems Inc.
The plastic sheets used for lining waste sites, ponds or lagoons are typically constructed out of a plastic material, such as polyethylene. Such plastic sheeting is available in varying thickness, width, and length. For example, Gundle Lining Systems, Inc., Houston, Tex. provides 250 foot long rolls of 100 mil thick, 22.5 feet width, high density polyethylene plastic sheeting under the label "Gundline HD" for use in such liner applications.
Next, if desired, a layer of heavy plastic netting, such as, "Gundnet" or "Geonet", or another filler material is placed on top of the liner sheeting and a second layer of plastic sheeting can be installed. The plastic netting or filler material serves to separate the two plastic sheeting layers.
The liner can then be covered, if desired, with a protective layer of earth to provide protection of the liner from puncturing and to help keep the liner in place. The waste, liquid, sludge material or the like is then placed on top of the plastic sheeting which is lining the reservoir, lagoon or pond.
As an additional step prior to covering the liner and introducing the waste material, pipes can be adapted to extend through the liner or liners to facilitate the collection and movement of the contained wastes from the lined containment area to a storage tank or other storage area. The pipe, such as plastic pipe, is inserted at desired locations in the liner. For example, the pipe is typically inserted horizontally through the sidewalls of the liner at the lowest point in the pond or reservoir. However, the insertion of pipe through the liner can damage or potentially damage the seal created by the liner. Particularly where hazardous wastes are involved, even the potentiality of any leak in the plastic liner of the waste pond will cause concern that the liner is not functioning properly. Thus, the ability to test and verify the sealability of the liner at the location of the pipe insertion is of considerable importance, both prior to and after the waste is first introduced into the liner. For example, state environmental regulations, such as those of Pennsylvania, require the testing of the joints formed where pipe penetrates through the waste liner.
Pipe penetration systems have been employed in liners in the past where a "pipe boot" is inserted through the liner and is then welded to the liner. This pipe boot serves as a sleeve for longer lengths of pipe which may be inserted therethrough and sealed thereto. The pipe boot resembles a "top hat" in that it comprises a short length of liner formed into a tube serving as the sleeve portion. One end of this tubular liner is flanged at such an angle to allow the remaining sleeve portion of the pipe boot to remain parallel to the liner sidewall it passes through. A square skirt of additional plastic liner material, having a width larger than the diameter of the flanged end of the tubular liner, is then cut so that it has an opening through its center slightly larger than the outer diameter of the tubular liner used for the pipe boot. This square skirt is then inserted over the tubular liner until it abuts the flanged end of the tubular liner. The skirt is then welded on one side to the sleeve portion of the tubular liner, and also on the other side to the flanged portion of the tubular liner. The flanged end of the pipe boot is then placed on the side of the liner which will contact the waste, and aligned over an opening in the liner of approximately the same size as the skirt portion of the pipe boot. The skirt portion of the pipe boot is then welded to the liner using known techniques. Plastic pipe can then be inserted through the sleeve of the pipe boot and then welded, clamped or otherwise sealed to the sleeve.
Use of the pipe boot configuration described above creates difficulties in testing and verifying the integrity and soundness of the seal or seals created between the pipe boot, skirt and the liner or liners, as well as, the seal created between the sleeve portion of the pipe boot and the pipe extending therethrough. Efforts have been made to field test the seals created in the pipe boot configuration. However, such efforts have been unsuccessful in that there is no practical way to apply pressure to the seals in order to test their intactness. For example, attempts have been made to build a dam around the installed pipe boot, and then to fill the dam with water to create a pressure head around the seals; however, this method did not work. Further attempts to test the pipe boot seals resulted in damage to the pipe boot itself.
Furthermore, it is difficult to visually detect any tears, rips, cracks, perforations, punctures or other potential leak forming channels in the seal areas around the pipe boot.
In accordance with the present invention, a method and apparatus are provided which will allow for penetrating a moisture impervious thermoplastic sheet or liner, particularly suitable for lining reservoirs, hazardous waste disposal sites, outdoor fluid containment areas and other similar applications, with a pipe penetration adapter without damaging the sealing characteristics of the liner, and in such a way as to also allow field testing of the sealability of the liner after the installation of the adapter.